title: Identification and functional analysis of phosphorylation residues of the Arabidopsis BOTRYTIS-INDUCED KINASE1.
abstract: Arabidopsis BOTRYTIS-INDUCED KINASE1 (BIK1) is a receptor-like cytoplasmic kinase acting early in multiple signaling pathways important for plant growth and innate immunity. It is known to form a signaling complex with a cell-surface receptor FLS2 and a co-receptor kinase BAK1 to transduce signals upon perception of pathogen-associated molecular patterns (PAMPs). Although site-specific phosphorylation is speculated to mediate the activation and function of BIK1, few studies have been devoted to complete profiling of BIK1 phosphorylation residues. Here, we identified nineteen in vitro autophosphorylation sites of BIK1 including three phosphotyrosine sites, thereby proving BIK1 is a dual-specificity kinase for the first time. The kinase activity of BIK1 substitution mutants were explicitly assessed using quantitative mass spectrometry (MS). Thr-237, Thr-242 and Tyr-250 were found to most significantly affect BIK1 activity in autophosphorylation and phosphorylation of BAK1 in vitro. A structural model of BIK1 was built to further illustrate the molecular functions of specific phosphorylation residues. We also mapped new sites of FLS2 phosphorylation by BIK1, which are different from those by BAK1. These in vitro results could provide new hypotheses for more in-depth in vivo studies leading to deeper understanding of how phosphorylation contributes to BIK1 activation and mediates downstream signaling specificity.
authors.affiliation: College of Life Sciences and Tianjin State Laboratory of Protein Science, Nankai University, Tianjin, 300071, China.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Xu
authors.forename: Xiaochao
authors.initials: X
authors.lastname: Wei
authors.forename: Limin
authors.initials: L
authors.lastname: Yan
authors.forename: Dan
authors.initials: D
authors.lastname: Liu
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ma
authors.forename: Yu
authors.initials: Y
authors.lastname: Guo
authors.forename: Chune
authors.initials: C
authors.lastname: Peng
authors.forename: Honggang
authors.initials: H
authors.lastname: Zhou
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Lou
authors.forename: Wenqing
authors.initials: W
authors.lastname: Shui
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D015398:Signal Transduction; D013912:Threonine / Q000235:genetics
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; D013912:Threonine; C509522:BIK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases